Process for forming earthenware from pulverized material



mt 1m 7 H. R. STRAIGHT PROCESS FOR FORMING EARTHENWARE FROM PULVBRIZED MATERIAL Dec 30 Patented 0a. 12, 1926. a

UNITED STATES PATENT OFFICE.

HALVER R. STRAIGHT, OF ADEL, IOWA.

Application filed December 30, 1924. Serial No. 758,896.

This invention relates to the manufacture of earthen ware.

My object is to provide an improved process for the manufacture of earthen ware so that the drying of the plastic material may be very rapidly accomplished at a very low cost, and at the same time materially decrease the loss of ware through warping and cracking during the drying period.

A further object is to provide a new process for treating the material as it is being formed into plastic condition by mixing a gas under pressure with the pulverized material before it has'been made plastic, and during the time in which it is being made plastic, for the purpose of expelling the air withinthe material, the gas being applied under heated condition so that as the material cools, condensation will take place, permitting the material to shrink and to have a greater density and-higher tensity.

In the drawings, 1 have illustrated a diagram of some of the apparatus for carrying out the novel steps of my improved process,

-. in whichthe numeral 10 indicates a base for supporting what is commonly termed the pug mill 11, said mill being in the form of a trough having a hopper 12 at one end and a longitudinally extending shaft 13 through the body portion of said trough. The said shaft is provided with plunger blades 17, which are for the purpose of mixing and pugging the material, as the said shaft 13 is rotated by means of suitable gear mechanism 15.

At the delivery end of the pug mill 11 is the tile forming machine 16 provided at its delivery end with the usual die 17. Themi ll 16 is designed to receive the material from the mill 11'. The material from the mill 16 is delivered to the tile cutter platform 18, all of which are of the usual construction now in common use.

At the receivinglend of the pug mill,,I have provided the hopper 12, which is provided with a delivery chute 19, by means of which pulverized material may be fed to the said hopper. Through the lower end of the hopper 12, I have provided a stem pipe 20, the inner end of which has an upwardly extending nozzle portion 21. The pipe 20 is provided with a :control valve 22 and its outer end connected to a steam generator 23 capable of producing steam under considerable pressure.

\ Adjacent to one side of the pug :mill, I

the operation of the pug mill 11.

have provided a hot water heater 24, which may be of any of the commercial types now in use, and provided with an outlet pipe 25 which is also provided with a control valve 26. The discharge end of the pipe 25 extends into the pug mill 11 at a point near the hopper 12. l

Pulverized shale or similar material may be fed to the hopper '12, through the chute 19, in such quantities as to keep the said hopper substantially full at all times during After the hopper 12 has been filled, as illustrated in the diagram, superheated steam is then turned into the pulverized shale which will at first condense near the nozzle 21, butafter the steam has been applied a short time, it

heats the material around the said nozzle and W111 gradually work upwardly through the pile of pulverized material within the hopper, so that the material within the lower end of the hopper becomes somewhat dry. The air within the spaces between the particles of pulverized material will be expelled and pass upwardly through the pile of ma terial and out through an opening 27 in the top of-the hopper, or the hopper may be left open at the top, if so desired.

After the material within the hopper has become heated-to a temperature considerably abovethe vapor point of steam, the pug mill 11 will then be thrown into operation and material willbe fed downwardly through the hopper. The hot water from the tank 24: may then be injected into the pug mill,

said water being at a temperature near the boiling point. The material will then be worked into a plastic condition in the usual manner, and will be delivered to the tile forming machine 16 while at a temperature near, or slightly below, the boiling point of water. I V The material is then delivered through the die 17 to the cutter table 18, after which it is cut into tile or brick in theusual manner, and delivered, while hot, to the drier kiln. The temperature of the air within the drier kiln should be somewhat less than the temperature of the tile as it enters the kiln, the ware being moved through the kiln ata comparatively slow and uniform rate, and at a velocity suflicient to remove the moisture from the ware as it is being driven off.

The steam from the nozzle '21 should be introduced in quantities and the capacity of the hopper should be such that the material in the lower end of the hopper will always be hot, while the material in the upper end of the hopper will always be at a temperature below the point of condensation, so that no steam will escape through the top of the pile of material, which will be prevented by coming in contact with the cooler material on the top and condensing. This enables the operator to utilize all of the heat units of the steam for heating purposes, and at the same time supply a certain amount of moisture to the material.

'It will be seen that by using superheated steam, the temperature of the material within the hopper 21 may be increased considerably above the boiling point of water, and when the heated water is introduced, the material may be delivered to the dies at a temperature near the boiling point. This will greatly assist in preventing air from entering the material as it is being worked by the pug mill and the moulding machinery.

By this method it will be seen that the ware may be made to dry much quicker and more uniformly than can be done by the common practice, which consists in mixing the pulverized material with cold water at about atmospheric temperature. When this is done, the ware has to be placed in a drier in which the drying medium, such as air, is raised to a temperature considerably above the ware. If an attempt is made to decrease the time in which the drying takes place, to any extent, the outer surface of the ware becomes heated above the temperature of the inner portion of the ware, and shrinks and cracks, and also causes warping. Inasmuch as the ware does not conduct the moisture from the center to the outer surface as fast as it is removed from the outer surface, it will be seen that a considerable time will be required to heat the inner portion of the ware to the desired temperature for completing the drying of the same. While with my improved process, as the material is heated either by superheated steam or other heated gases before and while it is going into the plastic condition, and is moulded and formed while heated, and delivered to the drier at a higher temperature than the drying atmosphere, drying of the ware will be very rapid. due to the fact that it is initially heated to a high temperature.

If the drying medium is at a slightly lower temperature than the ware when it is initially introduced into the kiln, it will be seen that cracking and shrinking of the outer surface of the ware will be impossible, due to the fact that the outer surface will not dry any faster than the inner surface, on account of the moisture, being expelled from the ware, having a tendency to vaporize or condense as it comes in contact with the slightly cooler medium. The medium, however, might be maintained at almost the same temperature as the ware. The temperature of the drying medium would have to vary some what with the different kinds of materials employed.

1t is a well known fact that the greatest shrinkage in the Ware takes place while the first part of the moisture is being given off. After a larger portion of the moisture has been removed from the ware, the tempera-- ture of the drying medium of the kiln might be increased above that of the ware, for the purpose of finishing the drying process, which is better accomplished with a considerably higher temperature than is advisable on the initial drying.

It will be seen that by heating the pulverized material and injecting a heated gas, such as superheated steam, into the same before it is made plastic, a large amount of free air will be driven from the material, and the mass will become more dense as it is pugged and worked through the forming moulds or dies, which will result in a prodnot having a considerable greater density than is possible by the previous method, due to the fact that the free air in the material is not extracted to any great extent by the pressure of the die or moulding apparatus, which results in a material which is somewhat porous, which greatly decreases the tensile strength of the ware after it is burned. This ware has somewhat the nature of grained wood or similar substance, and has a tendency to split or break along the seams. These seams are formed by pockets of air within the material as the plastic material is being kneaded and formed from an irregular shape into a symmetrical form.

Another advantage of my method is that by applying hot water to the material to reduce it to a plastic body, I find that it requires about fifteen percent less water, when the material is worked hot, than when hot water is applied instead of cold water to produce the same plasticity, and consequently the drying process is further hastened due to the fact that it is necessary to evaporate fifteen percent less water than when the mixture is'worked cold.

Thus it will be seen that I have provided an improved process which will greatly reduce the length of time required to dry the plastic material, and which will result in a lower cost of production, and at the same time add considerably to the quality of the ware after it has been burned.

I claim as my invention:

1. The method of forming ware from pulverized material to be burned from shale and the like, which consists in first pulverizing the shale to a granular state, then subjecting the pulverized material to superheated steam of such quantities as to raise the temperature of the mixture near or above the boiling point of water, then in- Ill) troducing Water, pugging to the desired consistency, moulding while hot, and drying.

2. The method of forming ware from pulverized material to be burned from shale and the like, which consists in first pulverizing the shale to a granular state, then heating the material to a comparatively high temperature, then introducing water and mixing the water and said material to a plastic condition, moulding while hot, and drying.

3. The method of forming ware from pulverized material to be burned from shale and the like, which consists in first pulverizing the shale to a granular state, then heating the material to a comparatively high temperature, then introducing water and mixing the water and said material to a plastic condition, moulding while'hot, and drying in a kiln having a circulating drying medium of a temperature slightly less than the temperature of the ware introduced therein.

4. The method of forming ware from pulverized material to be burned from shale and the like, which consists in first pulverizing the shale to a granular state, then heating the material to a comparatively high temperature, then introducing water and mixing the Water and said material to a plastic condition, moulding while hot, and drying in a kiln having a circulating drying medium of a temperature slightly less than the tempe ature of the Ware introduced therein until the ware has given ofi a portion of its moisture, then increasing the temperature of the drying medium above that of the ware to finish drying.

5. The method of forming ware from pulverized material to be burned from shale and the like, whichconsists in pulverizing the shale to a granular state, introducing the same into a hopper, and subjecting the material within the hopper to superheated steam of such quantities as to bring the temperature of the material within the hopper to the boiling point or above of water, then feeding the material to a pug mill and introducing water and forming to plastic condition, then feeding the hot plastic material to a moulding machine, moulding and forming the material into blocks or the like while hot, and introducing the hot plastic blocks to a drying kiln, the depth of the material hopper being such that the steam submitted to the material in such quantities that the portion of the material within the lower part of the hopper will be heated, while that in the upper portion will be at a normal temperature to cause condensation of the steam near the upper portion of the material within the hopper.

6. The method of forming ware from pulverized material to be burned from shale and the like. which consists in feedin the pulverized shale to a hopper, introducing a heated gas, which condenses at atmospheric temperatures, to the material within the hopper in such quantities that the material at the delivery end of the hopper will be heated at a temperature above the condensation point of the gas, while the material in the receiving end of the hopper will be retained at a temperature below the condensa tion point of gas, for the purpose of retaining and utilizing all of the heat units of said gas.

HALVER R. STRAIGHT. 

